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  3. 3. MYOPIA• Short sightedness• Myopia is a greek word meaning *close the eye*• Refractive error I• Parallel rays of light coming from infinity are focused in front of the retina.• Accommodation is at rest 3
  4. 4.  Mechanism of production• Axial• Curvatural• Positional• Index• Myopia due to excessive accommodation 4
  5. 5.  Optics of myopia• Far point is finite (In front of the eye)• Emmetropic eye it is at infinity• Higher the myopia the shorter the distance• Far point is 1mt from the eye ,there is 1D of myopia• Nodal point is further away from retina Accommodation need not develop normally resulting in Convergence insufficiency Exophoria 5
  6. 6. TYPES OF CLASSIFICATION• Clinical Classification• Degree of Myopia• Age of Onset 6
  7. 7. Clinical Classification• Congenital Myopia• Simple Myopia• Degenerative Myopia• Nocturnal Myopia• Pseudo Myopia• Induced Myopia 7
  8. 8. Degree of Myopia• Low Myopia(<3D)• Medium Myopia(3-6D)• High Myopia(>6D) 8
  9. 9. AGE OF ONSET• Congenital Myopia• Youth-Onset Myopia(<20 yrs of age)• Early Adult-Onset Myopia(20-40 yrs of age)• Late Adult-Onset Myopia(>40 yrs of age) 9
  10. 10. Congenital myopia Frequently seen in Premature babies Marfan’s syndrome Homocystinuria Increase in axial length Increase inOverall globe size Since birth, diagnosed at age 2-3 years If unilateral, as anisometropia, may develop amblyopia, strabismus Usually 8-10 D, remain constant Bilateral- difficulty in distant vision, hold 10 things very close
  11. 11.  Associated conditions Convergent squint Cataract Microphthalmos Aniridia Megalocornea Congenital Separation of retinaManagement Early Correction is desirable Retinoscopy under full cycloplegia Early full correction desirable Poor prognosis 11
  12. 12. • Simple / developmental myopia Physiological error not associated with any disease of the eye Etiology : Normal biological variation in development of eye Inheritence 12
  13. 13.  Associated factors Role of diet Theory of excessive near work 13
  14. 14.  Clinical picture Rarely present at birth Rather born hypermetropic, become myopic Begins at 7-10 years, stabilizing around mid teens Usually around 5D, never exceeds 8D 14
  15. 15. Symptoms Poor vision for distance Asthenopic symptoms develop due to dissociation between accommodation and convergenceConvergence weakness, exophoria, suppressionExcessive accommodation inducing ciliary spasm and artificially increasing the amount of myopia Psychological outlook 15
  16. 16.  Signs Large and prominent Deep AC Large, sluggishly reacting pupils Normal fundus, rarely crescent Usually doesnt exceed 6-8D• Retinoscopy under full cycloplegia 16
  17. 17. • Pathological / degenerative / progressive myopia Rapidly progressive associated with degenerative changes in the eye Etiology Rapid axial growth of the eyeball outside the normal biological variations of development Role of heredity Role of general growth process 17
  18. 18. Genetic factors General growth process More growth of retina Stretching of sclera Increased axial length Degeneration of choroid Degeneration of retina 18
  19. 19.  Symptoms Defective vision Muscae volitantes / floating black opacities 19
  20. 20. Signs EYE Large, prominent eyes simulating exophthalmos CORNEA large ANTERIOR CHAMBER deep LENS show opacities at the posterior pole due to aberration of lenticular metabolism and due to overstretching anterior dislocation may also occur 20
  21. 21.  VITEROUS degeneration,viterous liquefication,vitreous detachment present as WEISS REFLEX SCLERA thinning resulting in formation of STAPHYLOMA VISUAL FIELD DEFECTS show Contraction and in some ring scotomas present 21
  22. 22.  DISC Large in size Myopic Crescent on the temporal side of the disc Choroidal Crescent Supertraction of the retina Inverse myopia Myopic crescent situated nasally and supertraction of the retina temporally called as INVERSE CRESCENT Peripapillary Atrophy 22
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  27. 27. Treatment Optical treatment Appropriate concave lenses Minimum acceptance providing maximum vision 27
  28. 28. GuidelinesLOW DEGREES OF MYOPIA (Up to -6D) IN YOUNG SUBJECTS Defect should never be overcorrected and advised for constant use to avoid squinting and develop a normal ACCOMMODATION-CONVERGENCE reflex IN ADULTS Receiving spectacle for the first time,have the ciliary muscle that are unaccostomed to accommodate efficiently so that lens of slightly lower power(1 or 2 D) may be prescribed for reading,especially if engaged in to any greater extent.Above the age of 40 years,when accommodation fails physiologically, a weaker glass for 28 near work is essential
  29. 29. HIGH DEGREES OF MYOPIAFull correction rarely be tolerated so we attempt toreduce the correction as little as is compatible withcomfort for binocular vision. We prescribe the lenswith which the greatest visual acuity is obtainedwithout distress 29
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  31. 31. ADVANTAGES OF SPECTACLES Economical Allow incorporation of prism,bifocals,pal which can be used for the management of esophoria or any accommodative disorders accompanying myopia Spectacles require less accommodation than contact lens for myopia that likelihood of accommodative asthenopia or near point blur in patients approaching presbyopia may be less 31
  32. 32. DISPENSING SPECTACLES IN HIGH MYOPIA• High index lens materials• Lighter lens materials• Reduced eyesize of selected frames• Minus lenticular lens designs 32
  33. 33. ADVANTAGES OF CONTACT LENS• Contact lens provides cosmosis• Large retinal image size and slightly better visual acuity in severe myopia 33
  34. 34. SURGICAL TREATMENT RK Phakic IOL’S Epikeratophakia PRK RK LASIK PRK ISCR Phakic IOL’S LASIK ISCR 34
  35. 35. Photorefractive Keratectomy (PRK)• Involves direct laser ablation of corneal stroma after removal of corneal epithelium mechanically or using a laser beam.• Done using Excimer laser• MUNNERLYN EQN: depth of ablation (micrometer)=[diameter of optical zone(mm)]² × 1/3power(Diopter)• For myopic a large amount of ablation is done in central cornea than in the periphery.• Give good results for -2D to -6D of myopia 35
  36. 36. LASIK Laser Assisted In situ Keratomileusis• Method:Anterior flap of cornea is lifted with a keratome and excimer laser is used to sculpt the stromal bed to change the refractive error of eye• Corrects 0.5 to 12D of myopia and upto 8D of astigmatism• Guidelines:Age more than 18yrs BCVA better than 6/12 Stable refraction for last 1yr Absence of corneal disease & ectasia• Note:• (1) In no case the residual bed thickness after the ablation should measure 250microns so as to avoid central corneal ectasia• (2) Ideally the ablation should be done within 30sec of the preparation of flap 36
  37. 37. LASEK Laser subepithelial Keratomileusis• Indications:• Low myopia• Irregular astigmatism• LASIK complications in contralateral eye• Thin corneal pachymetry• Predisposition to trauma• Glaucoma suspect 37
  38. 38. • Method:• Simple inexpensive procedure that involves creation of epithelial flap after exposure to 18% alcohol for 25sec & subsequent replacement of flap after laser ablation 38
  39. 39. RK Radial Keratotomy• It refers to making deep corneal incisions(initially 16,now down to 4) in the peripheral part of cornea leaving about 4mm central optical zone• The incisions are made almost down to the level of Descemet’s Membrane• These incisions on healing flatten the central cornea thereby reducing its refractive power• For low to moderate degree of myopia(-1.5 to -6D of myopia) 39
  40. 40. Epikeratophakia• For high degree of myopia (upto 20D)• Method:• The epithelium is removed & then a pocket is fashioned under the edge of the remaining epithelium & into this is inserted the cryolathed donor homograft• Preserved material can also be used 40
  41. 41. NON CORNEAL INTERVENTIONS• (A) REMOVAL OF CLEAR LENS• We know that an aphakic eye is strongly hypermetropic• If an eye with an axial myopia of -24D is deprived of its lens it will become emmetropic without any correcting lens• Note:• Whenever surgery on clear lens is contemplated the eye is examined thoroughly for abnormalties like Raised IOP,Vitreous & retinal degeneration etc 41
  42. 42. • (b)Phakic intraocular lenses• An IOL of appropriate power is implanted inside the eye without touching normal crystalline lens thus without disturbing accomodation• Method can be used to correct both myopia & hypermetropia• Phakic IOL types:• PC IOL• Angle supported IOL• Iris claw lens 42
  43. 43. INTRA CORNEAL RING(ICR) IMPLANTATION• ICR implantation into the peripheral cornea approx.upto 2/3rd of stromal depth can also be considered for correction of myopia• It results in a vaulting effect that flattens the central cornea decreasing the myopia• The procedure has the advantage of being reversible 43
  44. 44. For Further Queries Contact :Ms. Priyanka SinghHead – Optometry ServiceEmail – 44
  45. 45. Thank you 45